Pre-Cushing's syndrome not recognized by conventional dexamethasone suppression-tests in an adrenal 'incidentaloma' patient

Pre-Cushing's syndrome has been recently diagnosed in 6-12% of patients affected with incidentally discovered adrenal masses. Some of these patients have been described to show transient hypoadrenalism after surgery, similarly to those affected with overt Cushing's syndrome. We studied a 70-year-old male patient with a large left adrenal mass, incidentally discovered, who displayed 24-h urinary free cortisol levels at the upper limit of the normal range, normal dexamethasone overnight and low-dose suppression tests and not suppressed ACTH levels, increased 17-hydroxyprogesterone response to ACTH stimulation and low upright plasma renin activity with normal serum aldosterone levels; furthermore, DHEAS level was low and 75 Selenium-cholesterol scintigraphy showed unilateral uptake concordant with the side of the mass. Soon after left adrenalectomy, he complained of acute hypoadrenalism requiring cortisol replacement therapy. ten months after surgery he is still hypoadrenal. Moreover, stimulated 17- hydroxyprogesterone and plasma renin activity in clino- and orthostatic posture have become normal. We propose that conventional dexamethasone suppression-rests may be not enough sensitive in this kind of patients and that in selected cases the absence of controlateral uptake at scintigraphy may be more reliable in predicting post-surgical hypoadrenalism.